The focus of this proposal is to define the systemic and local immune responses to administration of adenovirus (Ad) gene transfer vectors to normal humans. Although Ad vectors can transfer genes in vivo to a wide variety of organs, both humoral and cellular immune responses to Ad vectors present formidable hurdles to the effective use these vectors to treat human disease. In an attempt to circumvent these hurdles, a great deal of effort is being made to design Ad vectors "stealth" to the immune system, or to use immune suppressive drugs to limit host responses to Ad vectors. It is the central concept of this proposal that the definition of local and systemic immune responses to Ad vectors in normal humans will help in the effort to use Ad vectors to deliver therapeutic genes to humans with disease. It is the hypothesis of this proposal that intrabronchial administration of Ad vectors to normals will elicit local (lung epithelial) and systemic humoral and cellular immunity directed against the Ad vector, but that these anti-vector responses will be mild. In contrast, the systemic (but not lung) immune response generated by intradermal administration will be far more robust. To evaluate this hypothesis, a clinical study has been developed to define systemic and local immune responses to administration of an Ad vector to normal individuals. The vector to be used is Ad5CMV.Null2, an E1a-, partial E1b-, partial E3-, Ad vector that is "null", i.e., it contains an expression cassette with a promoter, but no transgene (to eliminate the variable of the immune response against the transgene). The vector will be administered to the bronchial epithelium or intradermal (one time, as well as repetitively, in ascending doses to different individuals), and the local (lung epithelial and dermal) and systemic humoral and cellular immune responses to the vector evaluated. These studies have the following objectives: (1) to define the local (lung epithelial) and systemic humoral and cellular immune responses to single and repetitive intrabronchial administration of a replication deficient Ad vector to normal individuals; (2) to define the systemic and lung epithelial humoral and cellular (cytotoxic T-lymphocyte) responses to single and repetitive intradermal administration of a replication deficient Ad vector to normal individuals; (3) to examine the differences in the local and systemic humoral and cellular immune responses to an Ad vector elicited by intrabronchial compared to intradermal administration of the Ad vector to normal individuals.